The autonomous cars They can not drive themselves if they are not able to "see" what happens in your environment. Depediendo capacity detection sensors and processing capacity of computer data, the car is able to perform tasks more or less by itself, more or less human intervention. Thus distinguished therefore up to five levels of automated driving.

For a car "you can see" radars, video cameras high resolution, high precision inertial GPS, ultrasonic sensors and lidar: different types of sensors in one way or another permit is required. Today we will explain what a LIDAR, one of the most common sensors in autonomous cars, and what it is.

LIDAR is an acronym

This we see here is a topographic LIDAR of the Leica brand, placed on a tripod (Photo by David Monniaux)

LIDAR is not a word as such, but an acronym. If we want to be respectful to technical and linguistic level, we should always use the acronym so that: LIDAR, in capital letters, without accents and without plural, because in the background they are a combination of acronyms or syllables.

Other acronyms such as RADAR, LASER, LED what has happened is that after years, and being widely used, these letters became commonly used words and acronyms are lexicarizaron. Therefore we can say radar, and plural radar, laser, and plural lasers and LEDs, and ledes plural (although the latter still generates some controversy).

LIDAR stands for 'Laser Imaging Detection and Ranging. " If a radar emits radio waves "ricochet" the objects, a LIDAR emits beams of infrared laser light, not dangerous at the conditions of use, that "ricochet" in objects

LIDAR stands for Laser Imaging Detection and Ranging. Curiously, it is an acronym which in turn is another acronym (LASER: Light Amplification by Stimulated Emission of Radiation). In Castilian we can be translated as LIDAR measurement system and object detection by laser.

In some other settings you have heard about them as a laser scanner. They are fairly common in works Topography, Geology, architecture and civil engineering. The of this type come to be very similar in appearance to a theodolite or a total station, and are also placed on a tripod, parked at a given vertex.

How does a LIDAR

This is the three-dimensional image point cloud that is capable of "see" real-time prototype Ford Mondeo autonomous thanks to 4 LIDAR Velodyne HDL-32E. The color change visually indicates the height above ground level (one of the people around the car detected by the LIDAR me)

LIDAR is a very basic way a focus emitting infrared laser beams (And therefore not visible), and a lens infrared receiver able to see these laser beams. In the conditions of use they are not dangerous to eyes, tanquilo.

Although there are some fixed LIDAR, for example the windshield basic models, is it a typical device rotates 360 degrees on itself to cover the entire environment.

Laser beams that are emitted impact on objects, they reflect (that is to say, "ricochet"), And become reflected rays are detected by the lens. So that we understand: a radar emits radio waves "ricochet" objects on a SONAR emits acoustic waves (ie sound) that "ricochet" on objects, and LIDAR emits light rays "ricochet" on objects.

Here we see a sensor unit composed windshield (a Volvo City Safety): the iquierda, see lenses laser beam emitting and receiving infrared lens LIDAR; in the center we see a video camera for recognition and pedestrian lane lines, with thermal filaments for defogging and deicing; on the right we see the light and rain sensor for automatic headlamp and wiper

Thus the processor LIDAR get a point cloud environment, with which the computer processes dimensional image in real time, which is constantly updated and in which the objects move. The most important points of this cloud is that each point is known for its precise position in space and the distance to it.

With a LIDAR can know in real time the precise position of millions of points, and the distance between each point and the focus of the LIDAR

This has been considered very useful in autonomous cars, it not only allows the computers indentificar objects, but you know exactly the distance that is each of them high accuracy (By measuring the time it takes for each laser beam going and return).

This way you can anticipate situations that will occur (eg the movement of other vehicles or pedestrians whose path will intersect with ours), or to determine whether there is danger of touching or hitting against something.

Types of LIDAR

This is one of the first prototypes of autonomous car of Google, a second-generation Toyota Prius. And other sensors, high ceiling, on a structure for elevating further and have a better visual, is a LIDAR Velodyne HDL-64E

Car several types of LIDAR. On the one hand we have the LIDAR windshield fixed rate. They consist of a rather compact unit with a lens for emitting the laser beams and a lens to capture the reflected beams.

They are placed on the top of the windshield in front of the mirror, for a better visual. Sometimes in the LIDAR unit it is combined with a video camera for recognition rail lines, recognition of pedestrians or traffic signs. They are primarily used for systems autonomous emergency braking, for example Volvo or Ford often use this type lidar.

There are different types of LIDAR: generally are either expensive or very expensive. Therefore, and because it is harder to integrate them into the design of the car, not all manufacturers choose them

On the other hand we have the LIDAR swivel 360 degrees. They are the ones that I have explained before, and basically is the adaptation of LIDAR topographic type for use in a car. The leading manufacturer today is Velodyne, and in a previous article I talked about him.

Three models LIDAR Velodyne brand (from left to right): HDL-64E, 32E and HDL-VLP-16 ( 'Puck')

From Velodyne They are the first LIDAR you used Google for years in their prototypes of autonomous cars. Already in 2012 we told you how the autonomous car of Google, article that continues today, and can also read for further information works.

Nowadays Google still using LIDAR: It's that kind of mushroom placed above the roof of the car, which in successive redesigns try to hide or integrate into the design. LIDAR is the largest model HDL-64E.

The lens 64 emits laser beams and turns on itself permanently 360 degrees, 900 rpm, to monitor the entire environment of the car, with up to 2.2 million points per second. It has a range of 50 m to 120 m and pavement for vehicles, pedestrians and trees. A unit in principle is enough. This model is also the most expensive, priced around $ 75,000 (about 63,700 euros, to change, plus VAT).

Here is a prototype Ford Mondeo autonomous hybrid (first generation). We see you at the top of the roof on a steel structure similar to a roof rack four LIDAR Velodyne HDL-32E. In the second generation are used LIDAR compact VLP-16 and camcorders.

Anyway Velodyne has developed smaller and economic LIDARFor example in the first prototype Ford autonomous Mondeo, which also will explain in detail how it works in 2014, 4 units of the model used HDL-32E. Each emits laser beams 32, also rotate about themselves 360 600 rpm, with up to 0.7 million points per second. The range is up to 80 to 100 m for vehicles, pedestrians and trees. All four are processed in total more than 2.5 million points.

Google, Ford, Toyota / Lexus, Nissan and Volkswagen have used different types of LIDAR in their prototypes of autonomous cars

The latest model is the most compact and inexpensive. It is called VLP-16. There are three variants: Puck, Puck Puck Lite and Hi-Res. 16 emits laser beams 360 degrees, covers up to 0.3 million points per second and reaches 100 m range. Its price is $ 7,999, that change come to be direct about 6,800 euros (plus VAT).

This type of LIDAR very compact is in which has been based for example Volkswagen imagining the prototype Volkswagen I.D. concept, a compact sedan, 100% electrical and autonomous driving. On the roof, in each of the four corners, four compact cylindrical hide LIDAR concealable on the roof itself. When driving in manual mode are hidden, but when automated driving mode is activated rise, protruding from the ceiling, and have visual to operate.

This is the prototype Volkswagen I.D. concept. On the roof we can see the four cylindrical compact LIDAR deployed, one at each corner (with a soft, 'molona' electric blue light). You could employ a type of LIDAR very similar to Velodyne VLP-16

Not all car manufacturers decide to use LIDAR 360 degrees as their prototype sensors autonomous cars (For its price, or difficulty aesthetic integration). Some prefer to use multiple video cameras, high-resolution stereoscopic often supplemented with different radar range and opening. I'll talk about these alternatives to LIDAR.

pictures | David Monniaux (Wikimedia CC)
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